Collapsible propeller for airplanes



April 3, 1940. H. A. DORNER COLLAPSIBLE PROPELLERV FOR AIRPLANES Filed May 8, 1939 512v. hwwmwwngwww 111M.

INVENTOR.

B HERMANN I.A. DORNER ATTORNEYS Patented Apr. 23, 1940 UNITED STATES PATENT OFFICE Application May 8, 1939, Serial No. 272,505 In Germany June 30, 1936 2 Claims.

The invention relates to collapsible propellers for airplanes being more particularly designed for use in connection with airplanes utilizing muscular power, or for gliders having auxiliary motors. It is the object of the invention to obtain a construction in which the blades of the propeller, when in collapsed position, will offerv but slight resistance to the movement of the plane. It is a further object to reduce the initial effort required in imparting rotary motion to the propeller shaft and in accelerating the same to a speed at which the blades will be effective in propelling the plane. Still further, it is an object to automatically and quickly effect the transition from collapsed to operative position of the blades and also to quickly collapse the blades when no longer needed for propulsion. With these objects in view, the invention consists in the construction as hereinafter set forth.

In the drawing:

Figure 1 is an elevation of the air propeller with the blades in collapsed position;

Figure 2 is a similar view at right angles to Figure l; 3

Figure 3 is a similar view showing the blades in operative position;

Figures 4 and 5 are enlarged views similar respectively to Figures land 2, and illustrating the streamlined housing;

Figure 6 is a cross section on line 66 of Figure 2.

Generally described, my improved collapsible air propeller comprises a rotary shaft, preferably tubular, a plurality of blades and a pivotal mounting for the blades upon the shaft permitting the arrangement of the same substantially parallel to the axis of rotation, as shown in Figures 1 and 2, or at substantially right angles to said axis, as shown in Figure 3. In the collapsed position, Figures 1 and 2, the center of gravity of each blade is slightly eccentric to the axis of rotation so as to be subject to unbalanced centrifugal forces tending to swing the blades outward. Such movement is, however, resisted by a counterbalancing spring, so that a predetermined rotational velocity must be attained before the blades will open. As the blades move outward the centrifugal force is progressively increased with the result that the blades Will quickly move to the fully extended position. The counterbalancing spring may be conveniently enclosed within re tubular shaft while the pivotal mounting is enclosed in a streamlined housing which minimizes air resistance. Thus, in collapsed position the'blades will offer but slight resistance to the forward movement of the plane or its operation as a glider. Moreover, the resistance to initial rotation and acceleration of the propeller shaft and blades is comparatively slight until the outward movement of said blades takes,place, whereupon they are quickly thrown into working position. 'This enables the pilot to start the propelling mechanism with relative ease and only when the propeller shaft is brought up to the minimum speed developing a centrifugal force suficient to overcome the spring pressure, will the blades suddenly and completely unfold.

As specifically illustrated, I and 2 are the blades provided respectively with hubs 3 and 4, which are pivoted on a common pin 5 secured in a bifurcated head member 6 mounted on the rear end of the propeller shaft 1. This shaft is preferably tubular and encloses within the same a rod 8 passing through an end bearing 8a and having sleeved thereon a coil spring 9. One end 20 of this spring abuts against the bearing8a, while the opposite end engages a threaded collar 90, through which the tension of the spring may be adjusted. In the rear of the bearing 8a there is secured to the rod 8 a head III which is coupled by links H and I2 with pivot pins l3 and It on rock arms l5 and I6 respectively connected to the blades 1 and 2.

The blades l and 2 in collapsed position have of a gradually tapering form from hub to rear end. They are also fashioned so that the center of gravity of each blade is slightly eccentric to the prolonged axis of the shaft 1, as indicated by the points IT and I8, Figure 6. Thus, centrifugal forces operating in each blade are slightly unbalanced so that after a certain rotational velocity is attained the resistance of the spring 9 will be overcome and the blades will move outward, to the position shown in Figure 3. Swinging beyond this position may be prevented by suitable stops, such as indicated at I9, Figure 4. Also, in collapsed position over-movement of the blades is prevented by stops 20 and 2 l. To minimize air resistance the connections between the blades and the shaft and spring are enclosed ,in astreamlined housing 22. This is cut away on opposite sides and at the rear end, as indicated at 23, to provide an opening for' the bladeswhen in collapsed position and also a pas- 50 sage for the movement of the blades to working position. I have, however, provided means for partially closing and streamlining the rear opening when the blades are extended so as to further lessen.- air resistance. This is accomplished by slides 24 arranged inside of the housing 22 and connected by links 25 with the head l0. During the outward movement of the blades the head 10 will be moved rearward which through the links 25, will move the slides 24 beyond the rear end of the casing 22 and into engagement with each other. I

To lessen the impact against the stops i9,

and 2|, I preferably provide shock absorbing Operation In operation, the parts are normally in the position shown in Figures 1, 2 and 4 to 6 inclusive, where the blades are in folded position extending rearward from the streamline housing extended position.

22. They will remain in this position as long as the shaft 1 is not revolved. When, however,

rotary motion is communicated to the shaft 1 by any suitable means (not shown) and this motion attains a certain predetermined angular velocity, centrifugal force will swing the blades I and 2 outward against the tension of the spring 9, whereupon the rapid increase in centrifugal force will quickly move the blades to their fully The blades will remain so extended as long as the shaft 1 is revolved, but when this motion ceases the tension of the spring 9 against the collar 9a will draw the rod 8 inward, thereby actuating the head I 0, and through the links H and I2 rocking the arms l5 and I6 to again return the blades into the position shown in Figures 1 and 2.

With the construction as above described, it will be obvious that the device may be readily mounted on an airplane or glider and will be available for intermittent use in propelling the machine, while during inactive periods it will offer but slight resistance.

What I claim as my invention is:

1. The combination with a rotary hollow propeller shaft, of a bifurcated member secured to and projecting rearward from said shaft, a pivot pin extending between the furcations at substantially right angles to the axis of said shaft, blades mounted on said pivot pin to extend in collapsed position rearward therefrom substantially parallel to the axis of said shaft, and means for yieldably holding said blades in collapsed position comprising an abutment bearing at the rear end of said hollow shaft, a head provided with a shank slidably engaging said abutment bearing, a spring sleeved upon said shank having one end engaging said abutment bearing, a head on said shank for'engaging the opposite end of said spring, rock arms for said propeller blades and links connecting said rock arms to said head, whereby the outward movement of said blades is resiliently resisted by said spring, and a substantially streamlined housing for the connections between said shaft and blades apertured for the outward movement of the blades.

2. The combination with a rotary hollow propeller shaft, of a bifurcated member secured to and projecting rearward from said shaft, a pivot pin extending between the furcations at substantially right angles to the axis of said shaft, blades mounted on said pivot pin to extend in collapsed position rearward therefrom substantially parallel to the axis of said shaft, and means for yieldably holding said blades in collapsed position comprising an abutment bearing at the rear end of said hollow shaft, a head provided with a shank slidably engaging said abutment bearing, a spring sleeved upon said shank having one v end engaging said abutment bearing, a head on said shank for engaging the opposite end-of said spring, rock arms for said propeller blades and HERMANN I. A. DORNER. 

